Iran’s “evil” leaders cannot be allowed to obtain nuclear weapons, President Shimon Peres said on Tuesday, calling the Islamic Republic’s nuclear ambitions the world’s single most important issue.

Peres’ comments came at the opening of the Herzliya Conference, which was attended by World Bank President Robert Zoellick, Czech Foreign Minister Karel Schwarzenberg, and former Greek Prime Minister George Papandreou.

Referring to Iran’s contentious nuclear program, the president called the issue “ours and the world’s central problem at this time, accusing Iran of attempting to achieve regional and “even global hegemony.”